The present invention relates, in general, to computer enhanced graphics and more particularly, to a method for selecting an area of a computer graphics screen.
One of the most fundamental operations of computer graphics is to select graphical objects to be worked on. Typically this area is defined as a rectilinear box that defines the area and selects objects within it in some way. The selection may be based on complete containment, partial containment, or contact between an object and the box. Another use for this box is to define a smaller region of the graphics screen to be displayed at a higher magnification. Typically a pointer controlled by an input means such as a mouse or stylus is caused to be moved about the screen under the control of the computer user. The box is defined by pressing a button which activates the input means. The cursor is then caused to move diagonally across the screen to define the area desired. A typical box selection method is described in "Superpaint 1.1" by R. L. Shnapp, published in 1988 by Silicon Beach Software, Inc., page 25 and 26. This example is used in a Macintosh computer system in which a mouse is used to move the cursor from one corner to the opposite corner of the desired area with the mouse button depressed. This causes a rectangle to be displayed which is continually resized to keep the second corner coincident with the cursor position. When the mouse button is released the boundary of the selected region is highlighted with a pattern of moving dashes. In this example, depressing keys on the computer keyboard will provide alternative methods for selection of shapes within the rectangle. This method for selection allows the user to readily adjust the width and height of the area, but does not allow the user to rigidly move the area horizontally or vertically.
The form of box definition used by the prior art is often awkward to use for defining the correct area of a graphical screen with a single action. If the first point is selected poorly, the selection process must be aborted to pick a different point. Typically once started the function that is invoked in this way is committed to completion before another box can be defined. Many such functions, such as completely resizing and redrawing the display screen may take many minutes or even hours to execute. However until the function finishes and the new information is shown on the display screen there is no reference by which to select a new box. Thus selection of the incorrect box can carry a severe penalty. With the increasing resolution and density of computer graphics displays picking the correct box on the first try becomes increasingly difficult.
There is a need for a method to define a resizable box on an area of a computer screen. The user must be able to move the defined area vertically and horizontally while simultaneously adjusting the width and the height. Since the select operation is one of the most frequently performed operations it is important that the operation be performed with a single keystroke.